Gas pressure alarm contactor



Oct. 20, 1936. v. B. PIKE 2,053,256

GAS PRESSURE ALARM CONTACTOR Filed May 11, 1935 2/ 2o f/B /9 Z 2 6 46 447 7 15 y 20 2/ Z lNl/ENTOR RP/K5 :9

ATTORNEY above atmospheric.

Patented Oct. 20, 1936 UNITED STATES PATENT OFFICE GAS PRESSURE ALARMCONTACTOR Application May 11, 1935, Serial No. 20,967

11 Claims. (01. 200-81) This invention relates toapparatus for use inconnection with the maintenance of cables and more particularly toapparatus for use with cables which are held continuously under gaspressure.

The object of the present invention is to provide an alarm contactor orpressure gauge in which a pressure element of the Bourdon tube type actsdirectly on the contact springs without the use of any intermediatemechanism.

The purpose of placing cables under continuous pressure is to preventthe entrance of moisture into the cable and to permit the locating ofsheath openings before the occurrence of insulation trouble. To providemeans for detecting loss from pressure in the cable, pressure contactorsare installed at points some distance apart along the cable; forexample, approximately two miles apart, and to connect these contactorsin parallel across a pair of wires which in turn are connected to asuitable alarm so that a warning is given automatically when thepressure falls below a predetermined value.

Cables are usually maintained at a pressure of 9.01:1.0 pounds persquare inch and the contactors are adjusted to operate at 6.0- *-0.5pounds per square inch, so that the alarm is given when the cablepressure falls to two-thirds of the value at which the cable is beingmaintained. These pressures are based on a standard cable temperature of60 F.

When the temperature of the cable changes, the pressure of the gas whichis confined within the cable also changes in accordance with wellknownphysical laws. It is therefore necessary 36 that the contactor be ofsuch design that its operating pressure is automatically corrected fornormal changes in the cable pressure caused by temperature changes.

Applicants improved contactor operates on the 40 principle of theBourdon tube, but differs from the ordinary arrangement in that the tubeis formed to include approximately 34.5 degrees of an arc, is supportedmid-way between its ends and that gas is sealed in the tube at apressure Insulatedly mounted on each end of the tube is a set screwwhich bears against a pair of contact springs which in turn areconnectedby means of wires to an alarm circuit. Under normal operatingconditions, that is, 50 when the pressure contactor is connected to acable under pressure, the pressure in the casing surrounding the Bourdontube is greater than the pressure in the Bourdon tube. Consequently, theends of the tube are forced toward each other 5 thereby holding thecontact springs apart and out of contact. However, upon a decrease ingas pressure due to a leak in the cable sheath, the pressure in theBourdon tube being greater than the pressure in the casing will causethe ends of the Bourdon tube to move apart thereby releasing 5 thepressure of the screws against the contact springs and 7 allowing thecontact members to engage each other thereby closing the alarm circuit.

Applicant has provided means for adjusting the 10 pressure at which thecontactor will operate. This is accomplished by. moving the contactspring assembly with respect to the ends of the Bourdon tube.

Applicant has also provided means for main- 15 taining the contacts inan open condition. This is desirable when the cable gas pressure is lowand it is necessary to make repairs to the cable sheath withoutinterfering with the normal operation of the remainder of the circuit.20

In general, applicants invention takes the form of a gas-tight chamberadapted for connection to a gas-filled cable or the like, a Bourdon tubehaving gas therein sealed above atmospheric pressure in said chamber andarranged to close a pair 25 of contact springs when the gas in thechamber falls below a certain predetermined value due to a drop in thecable gas pressure.

The invention will be more clearly understood from the followingdetailed description of one de- 30 sired embodiment thereof read withreference to the accompanying drawing.

Fig. 1 of the drawing is a plan view partly in section illustratingapplicants improved contactor in its operated position, that is, withthe contact springs closed due to the expansion of the Bourdon tube.

Fig. 2 is a partial sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is a fragmentary view of the contacting mechanism together with aportion of the Bourdon tube as it would appear with the device underpressure, that is, with the gas pressure in the chamber causing theBourdon tube to contract.

Fig. 4 is a schematic showing the manner in which the contactors areconnected to the alarm circuit.

With reference to Fig. 1 of the drawing, the gas pressure alarmcontactor comprises a casing l0 and a gas-tight cover H which is securedto the casing by means of the studs l2. The mechanism on the interior ofthe casing I0 operates on the principle of the Bourdon tube but differsfrom the ordinary arrangement, based on this principle, in that theBourdon tube I3 is formed to in- 5 clude approximately 345 degrees of anarc and is sealed with gas at a pressure above atmospheric. The Bourdontube 13 comprises two arcuate portions l4 and I5 which are supported bymeans of the bracket I6 which in turn is secured to the back wall I! ofthe casing l0.

Adjustably mounted on the interior of the casing I0 is a pair of contactsprings l8 and I9 to which the alarm circuit wires 20 and 2| areconnected. By means of the adjustment screw 22 and the spring 23 thecontact springs I8 and I9 may be moved forward or backward with respectto the ends l4 and I5 of the tube I3, thereby providing an adjustablemeans .for regulating the operation of the contacts for any given cablepressure. In order that no gas may escape around the adjustment screw22, a nut 24 is provided which bears against a shouldered and chamferedbushing 25, which in turn exerts pressure on the soft metallic bushing26 thereby preventing the escape of any gas by forming a tight sealaround the adjusting screw 22.

Located on the end portions [4 and I5 of the Bourdon tube l3 are a pairof set screws 21 and 28. These screws have insulated tips which bearagainst the contact springs I8 and I9, and are adjustably supported bymeans of the members 29 and 30.

Under normal conditions, that is, when a pressure is being maintained inthe cable the contact springs 18 and I9 are normally held opened asshown in Fig. 3. However, when a leak in the cable sheath occurs, andthe gas pressure decreases, the pressure in the Bourdon tube l3 willexceed the gas pressure in the casing I 0 of the contactor, therebycausing the end portions I 4 and I5 of the Bourdon tube l3 to expandcausing the contact springs IB and 19 to engage each other as shown inFig. 1. This closes the circuit and causes the alarm to operate as shownin Fig. 4. In this figure the two contactor-s 3| and 32 are connected inparallel across the alarm pair 33 and 34 which terminates in the alarmrelay 35, which when energized causes the bell 36 to operate.

Inasmuch as it is often necessary, in cable maintenance work, to rendera particular contactor inoperatable, it is necessary that some means beprovided for maintaining the contact springs in an open position. It isalso necessary that this means be operatable from the outside of thecontactor so that there will be no escape of as due to the removal ofthe cover H which would be necessary if some means were not providedwhereby the contact springs could be maintained in an open conditionfrom the outside of the casing.

Located on the lower portion of the contactor is an adjusting screw 31by means of which the arms 38 and 39 are caused to engage the bottom ofthe screw supporting members 29 and 30 on the end portions l4 and I5 ofthe Bourdon tube l3. When the adjusting screw 31 is turned in aclockwise direction, the arms 38 and 39 will engage the members 29 and30 and cause them to move toward each other thereby holding the contactsprings l8 and I! open thereby preventing the end portions I4 and l5 oithe Bourdon tube l3 from expanding and allowing the springs in and H tocontact.

The adjusting screw 37 is provided with righthand and left-hand threadedportions 43 and 44 which pass through and engage the arms 38 and 39,whereby the rotation of the adjusting .screw 31 will cause thearms 38and .39 to move toward or away from each other depending upon thedirection of rotation of the adjusting screw 31.

In order to prevent the leakage of gas from around the adjusting screw31 a soft metallic bushing 4| is held in contact with the body adjustingscrew 31 by means of the sleeve 40 and the nut 42, thereby providing agas-tight gland. A suitable mounting means 45 on the interior of thecasing is provided to act as a bearing for the adjusting screw 31.

The contactor casing 10' is provided with suit able fittings 46 and 41for connecting the contactor to the cable stub 48, which in turn isconnected to the cable sheath and to the alarm circuit wires in thecable (not shown).

Applicants contactor employs no pivot bearings or sliding parts inasmuchas the movement of the gas pressure element which is a Bourdon tubecomprising approximately 345 degrees of an arc is transmitted directlyto the contact springs. In previous designs the interconnecting partsbetween the Bourdon tube and the contact springs caused an undesirablevariation in their operation. This has been entirely eliminated inapplicants improved contactor.

The applicant has found that this improved contactor will operate atpressure variations within .005 pound per square inch whereas in thepresent types of gas pressure contaotors variations of .15 pound persquare inch are ordinarily found and much larger variations are common.

It is to be understood that various modifications and changes may bemade in this device without departing from the spirit of the invention.For example, applicant does not intend to limit himself to any definitepressure in the Bourdon tube.

What is claimed is:

1. A pressure contactor comprising a gas-filled sealed chamber, acontactor mechanism mounted therein, said contactor mechanism comprisinga pair of slidably mounted contact springs and a Bourdon tube in theform 01' an arc, the iree ends of said tube provided with adjustablemeans whichengage said contact springs.

2. A pressurecontactor comprising a gas-filled sealed chamber, acontactor mechanism mounted therein, said contactor mechanism comprisinga pair of slidably mounted contact springs and a Bourdon tube in theform of an are, said contact springs located between the free ends ofsaid tube and adapted to be engaged thereby.

3. A pressure contactor comprising a gas-filled sealed chamber, acontactor mechanism mounted therein, said contactor mechanism comprisinga pair of slidably mounted contact springs and a Bourdon tube in theform of an are, said Bourdon tube being sealed at a pressure aboveatmospheric, the free ends of said Bourdon tube having mount- .edthereon adjustable means for engaging said contact springs.

4. A pressure contactor mechanism comprising a gas-filled sealedchamber, a contacting mechanism mounted in said chamber and comprising apair of slidably mounted contact springs and a gas-filled Bourdon tubein the shape of an arc, the free ends of said Bourdon tube provided withadjustable means which bear against and actuate said contact springsupon movement of said tubes.

5. A pressure contactor mechanism comprising a gas-filled sealedchamber, a contactor mechanism mounted in said chamber and comprising apair of contact springs slidably mounted between the free ends of anarc-shaped Bourdon tube, the free ends of said tube provided withadjustable means which bear against and are adapted to operate saidcontact springs when a change in gas pressure in said chamber causes theBourdon tube to move.

6. A pressure contactor comprising a gas-filled sealed chamber, acontactor mechanism mounted therein, said contactor mechanism comprisinga pair of slidabiy mounted contact Springs, an arc-.

shaped Bourdon tube, the free ends of which are adapted to engage saidcontact springs which are located between the free ends of said tube andmeans for adjusting said contact springs.

'7. A pressure contactor comprising a gas-filled sealed chamber, acontactor mechanism mounted therein, said contactor mechanism comprisingan arc-shaped gas-filled Bourdon tube fixably secured at itsmid-portion, a pair of contact springs slidabiy mounted between the freeends of said Bourdon tube and adapted to be engaged by adjustable meanson the ends of said tubes.

8. A pressure contactor comprising a gas-filled sealed chamber, acontactor mechanism mounted in said chamber, said contactor mechanismcomprising a gas-filled Bourdon tube in the shape of an arc, a pair ofcontact members siidably mounted between the free ends of said are andin engagement therewith, and means associated with the free ends of saidBourdon tube for opening said contacts.

9. A pressure contactor comprising a gas-filled sealed chamber, acontactor mechanism mounted in said chamber, said contactor mechanismcomprising a pair of siidabiy mounted contact springs, a Bourdon tube inthe shape of an arc having its free ends engaging said contact springs,means associated with said contact springs for changing the position ofsaid contact springs with respect to the ends of the Bourdon tube.

10. A pressure contactor comprising a gasfilled sealed chamber, acontactor mechanism mounted in said chamber which comprises a pair ofsiidably mounted contact springs and a gasfilied Bourdon tube in directengagement therewith, said Bourdon tube acting directly on said contactsprings when movement is imparted thereto by a decrease in the gaspressure in said chamber.

11. A pressure contactor comprising a gasfiiled sealed chamber, a pairof contact members siidably mounted in said chamber, a Bourdon tube inthe shape of an are, associated with and adapted to actuate said contactmembers, said tube being rigidly secured at its mid-portion to saidchamber, and the free ends of said tube adapted to directly engage thecontact springs, said tube having gas sealed therein at pressure aboveatmospheric.

VERNON B. PIKE.

